RESUMO
Prostate cancer is considered to be one of the most hormone-dependent human malignancies. As a key mediator of hormonal response, the androgen receptor (AR) is believed to have an important role in the progression of prostate cancer. Mutations in the coding region of the AR gene have been found in both untreated and hormone-refractory prostate cancer, but the frequency of such mutations at different stages of the disease is poorly documented and even contradictory results have been published. In the present study, the frequency of AR gene mutations was determined in 30 locally recurrent and two metastatic hormone-refractory prostate tumours using the polymerase chain reaction (PCR), non-radioactive single strand conformation polymorphism (SSCP), and sequencing. The length of the polymorphic CAG repeat, which is inversely correlated with the ability of the AR to activate transcription, was also analysed as well as the GGC repeat. Twelve samples were known to contain an AR gene amplification. Altogether, one point mutation (Gly(674)-->Ala) and one microsatellite mutation (CAG(20)-->CAG(18)) were found, both in cancers containing the AR gene amplification. The mean lengths of the polymorphic CAG and GGC repeats were similar to those observed in the normal population. These results favour the view that mutations in the AR gene are rare in hormone-refractory prostate cancer and do not play an important role, at least, in local relapse. Instead, the amplification and consequent overexpression of the wild-type AR gene seem to be the most common alteration involving the AR in hormone-refractory prostate cancer.
Assuntos
Carcinoma/genética , Amplificação de Genes , Mutação , Proteínas de Neoplasias/genética , Neoplasias da Próstata/genética , Receptores Androgênicos/genética , Carcinoma/patologia , Humanos , Masculino , Mutagênese Sítio-Dirigida , Reação em Cadeia da Polimerase , Polimorfismo Conformacional de Fita Simples , Neoplasias da Próstata/patologia , Análise de Sequência de DNARESUMO
Two repetitive elements of the chicken CR1 family, each located in the 5' flanking region of the avidin-related genes Avr4 and Avr5, have been cloned and sequenced. Both elements are 721 bp in length with 72% identity to a CR1 consensus sequence. They had a 191 bp deletion in a region corresponding to the functional silencer regions previously detected within the CR1 elements upstream of the chicken lysozyme and apoVLDLII genes.
Assuntos
Avidina/genética , Galinhas/genética , Sequências Repetitivas de Ácido Nucleico/genética , Animais , Sequência de Bases , Clonagem Molecular , Sequência Consenso , Dados de Sequência Molecular , Sequências Reguladoras de Ácido Nucleico , Deleção de Sequência , Homologia de Sequência do Ácido NucleicoRESUMO
The gene encoding chicken egg-white avidin (Avd) was amplified from chromosomal DNA, cloned and sequenced. The entire coding region of preavidin (pre-Avd) containing four exons was identified by comparing the Avd gene (1119 bp) with the cDNA. It has a high identity percentage (91-95%) with the previously isolated Avd-related genes 1-5 (Avr1-Avr5). Interestingly, comparison of Avd with the Avr genes showed that the introns were better conserved (on average 97%) than the exons (90%). The Avd gene, as well as the cDNA, encodes a Gln residue at position 53 of the mature protein, which is in contrast to the previously determined amino-acid sequence.
Assuntos
Avidina/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Evolução Biológica , Galinhas , Clonagem Molecular , DNA Complementar/genética , Éxons , Genes , Íntrons , Dados de Sequência Molecular , Precursores de Proteínas/genética , Homologia de Sequência do Ácido NucleicoRESUMO
Using avidin cDNA as a hybridisation probe, we detected a gene family whose putative products are related to the chicken egg-white avidin. Two overlapping genomic clones were found to contain five genes (avidin-related genes 1-5, avr1-avr5), which have been cloned, characterized and sequenced. All of the genes have a four-exon structure with an overall identity with the avidin cDNA of 88-92%. The genes appear to have no pseudogenic features and, in fact, two of these genes have been shown to be transcribed. The putative proteins share a sequence identity of 68-78% with avidin. The amino acid residues responsible for the biotin-binding activity of avidin and the bacterial biotin-binding protein, streptavidin, are highly conserved. Since avidin is induced in both a progesterone-specific manner and in connection with inflammation, these genes offer a valuable tool to study complex gene regulation in vivo.
Assuntos
Avidina/genética , Galinhas/genética , Sequência de Aminoácidos , Animais , Avidina/química , Avidina/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Biotina/metabolismo , Clonagem Molecular/métodos , Sequência Conservada , DNA/genética , DNA/isolamento & purificação , Éxons , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Precursores de Proteínas/química , Precursores de Proteínas/genética , Pseudogenes , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/metabolismo , Mapeamento por Restrição , Homologia de Sequência de Aminoácidos , Homologia de Sequência do Ácido Nucleico , Estreptavidina , Transcrição GênicaRESUMO
Inflammation-mediated avidin gene expression in the chicken was studied using hybridization analysis, polymerase chain reaction (RT-PCR) and sequencing. The results indicate the presence of avidin mRNA in the oviduct and intestine after Escherichia coli infection. The mRNA for the inflammation-induced avidin was mainly encoded by the avidin gene, but the avidin-related genes, avr2 and avr3, were also transcribed at a low level in the oviduct and intestine, respectively. Because avidin is also induced in the chicken oviduct by progesterone, our results indicate a multifactorial regulation of avidin gene expression.
